The early works featuring Morgan do not elaborate her character beyond her role as a fay or magician. She became much more prominent in the later cyclical prose works such as the Lancelot-Grail and the Post-Vulgate Cycle, in which she is said to be the daughter of Arthur's mother, the Lady Igraine, and her first husband, Gorlois, Duke of Cornwall; Arthur is her half brother by Igraine and Uther Pendragon. Morgan has at least two older sisters, Elaine and Morgause, the latter of whom is the mother of Gawain and the traitor Mordred. In Sir Thomas Malory's Le Morte d'Arthur and elsewhere, she is married, unhappily, to King Urien of Gore and Ywain is her son. Though she becomes an adversary of the Round Table when Guinevere discovers her adultery with one of her husband's knights, she eventually reconciles with her brother, and even serves as one of the four enchantresses who carry the king to Avalon after his final battle at Camlann.

Later interpretations

The stereotypical image of Morgan is often that of a villainess: a seductive, megalomaniacal sorceress who wishes to overthrow Arthur. Contemporary interpretations of the Arthurian myth sometimes assign to Morgan the role of seducing Arthur and giving birth to the wicked Mordred, though traditionally Mordred's mother was Morgause, another sister. In these works Mordred is often her pawn, used to bring about the end of the Arthurian age. Starting in the later 20th century, however, some feminists adopted Morgan as a representation of female power or of a fading form of feminine spirituality supposedly practiced by the Celts or even earlier peoples. These interpretations draw upon the French romances which portray Morgan as a "benevolent figure" with extraordinary healing powers. This has led to Morgan's expanded role in feminist Arthurian literature such as Marion Zimmer Bradley's The Mists of Avalon, which goes so far as to give her credit for the major events of the traditional story.